In vitro effects of melatonin on [3H]muscimol binding in rat brain.

The possible interaction of melatonin with the GABAergic system at the receptor level was investigated. The effect of melatonin on the binding of the GABA agonist, [3H]muscimol, in crude synaptic membrane preparations was assayed. In fresh membrane preparations, melatonin increased [3H]muscimol binding in the rat striatum and frontal cortex. Treatment of membrane preparations with Triton X-100 appeared to abolish or depress the enhancing effect of melatonin. The use of Tris HCl as buffer appeared to be more effective than Tris-Citrate buffer suggesting a possible important ionic effect. The present findings suggest that melatonin is capable of enhancing [3H]muscimol binding in vitro, perhaps at the benzodiazepine-GABA-receptor-ionophore complex.